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Cranberry Pest Control: Early Rot (Scald) of Cranberry and Blast of Blossoms and Young Fruit, A3352

A3352
CRANBERRY PEST CONTROL
Early Rot (ScaId) of Cranberry
and Blast of Blossoms and Young Fruit
Phyllosticta vaccinia Earle
Donald M. Boone and Gregory J. Weidemann
Early rot was one of the first
cranberry diseases to be described
and was thought to be caused by
Guignardlh vaccinia Shear
fBotryosphaen'a vaccinia (Shear) Barr)
which has been shown to have
Phyllosticta elongate Weidemann as
the imperfect or gonadial stage. However
Phyllosticta vaccinia Earle is a
distinct species and the true causal
organism of the disease, P vaccinia
apparently is restricted to cranberrygrowing
areas in New Jersey and
Massachusetts and causes many of
the diseases formerly attributed to B.
vaccinia.
Early rot is largely a problem in areas
that have long growing seasons and
high summer temperatures. This
disease does not affect Wisconsin's
cranberry industry. It also does not
occur on the West Coast.
However New Jersey cranberry
growers, and to a lesser extent those
of Massachusetts, can sumer appreciable
losses due to early rot and
blossom and young fruit blast. Without
protection by fungicides a high
proportion of the crop can be lost on
occasion in some bogs. This fungus
also can attack leaves and may kill
plants in young beds due to extensive
leaf and stem injury.
The diseased area on cranberries is
frequently marked by concentric rings
giving a bullseye pattern.
Infected young cranberries usually
shrivel and become covered with
cardia.
my
Symptoms and Signs
The first indication of infection by P
vaccinia is the appearance of a small,
light-colored, watery spot on the
cranberry fruit. Under favorable conditions,
this spot enlarges fairly rapidly,
usually in a concentric manner until
the whole berry becomes soft. Frequently
the diseased area consists of
dark, concentric rings giving a bell'seye
pattern. However the cranberry
may show little discoloration if the rot
develops rapidly.
Ordinarily, there is no indication of the
fungus itself on the surface of
diseased, fully developed cranberries.
However cranberries infected before
they are half grown usually shrivel,
become blackened, and are covered
with fungal pycnidia. This form of the
disease is called ''blast'' or sometimes
''blight'' if very young cranberries are
attacked about the time the blossoms
fall .
Occas/bna//y shoot tips and flowers
are killed and turn brown.
Irregular reddish-brown spots develop
on infected leaves and bear pycnidia
of the fungus.
Occasionally shoot tips and flowers
are killed and turn brown. When
leaves become infected, irregular
reddish-brown spots cover part of the
leaf and bear fungal pycnidia on the
upper leaf surface. However shoot
blight and leaf spotting are usually of
minor importance.

A3352
CRANBERRY PEST CONTROL
Early Rot (ScaId) of Cranberry
and Blast of Blossoms and Young Fruit
Phyllosticta vaccinia Earle
Donald M. Boone and Gregory J. Weidemann
Early rot was one of the first
cranberry diseases to be described
and was thought to be caused by
Guignardlh vaccinia Shear
fBotryosphaen'a vaccinia (Shear) Barr)
which has been shown to have
Phyllosticta elongate Weidemann as
the imperfect or gonadial stage. However
Phyllosticta vaccinia Earle is a
distinct species and the true causal
organism of the disease, P vaccinia
apparently is restricted to cranberrygrowing
areas in New Jersey and
Massachusetts and causes many of
the diseases formerly attributed to B.
vaccinia.
Early rot is largely a problem in areas
that have long growing seasons and
high summer temperatures. This
disease does not affect Wisconsin's
cranberry industry. It also does not
occur on the West Coast.
However New Jersey cranberry
growers, and to a lesser extent those
of Massachusetts, can sumer appreciable
losses due to early rot and
blossom and young fruit blast. Without
protection by fungicides a high
proportion of the crop can be lost on
occasion in some bogs. This fungus
also can attack leaves and may kill
plants in young beds due to extensive
leaf and stem injury.
The diseased area on cranberries is
frequently marked by concentric rings
giving a bullseye pattern.
Infected young cranberries usually
shrivel and become covered with
cardia.
my
Symptoms and Signs
The first indication of infection by P
vaccinia is the appearance of a small,
light-colored, watery spot on the
cranberry fruit. Under favorable conditions,
this spot enlarges fairly rapidly,
usually in a concentric manner until
the whole berry becomes soft. Frequently
the diseased area consists of
dark, concentric rings giving a bell'seye
pattern. However the cranberry
may show little discoloration if the rot
develops rapidly.
Ordinarily, there is no indication of the
fungus itself on the surface of
diseased, fully developed cranberries.
However cranberries infected before
they are half grown usually shrivel,
become blackened, and are covered
with fungal pycnidia. This form of the
disease is called ''blast'' or sometimes
''blight'' if very young cranberries are
attacked about the time the blossoms
fall .
Occas/bna//y shoot tips and flowers
are killed and turn brown.
Irregular reddish-brown spots develop
on infected leaves and bear pycnidia
of the fungus.
Occasionally shoot tips and flowers
are killed and turn brown. When
leaves become infected, irregular
reddish-brown spots cover part of the
leaf and bear fungal pycnidia on the
upper leaf surface. However shoot
blight and leaf spotting are usually of
minor importance.